Was disappointed in the Sky King Calf Machine

Anyone tried it? I just bought it and it was easy. I’m not even trying to increase my vertical. I’m just trying to train my calves. I did 50 slow and controlled reps the first time I used it. It must not be very hard if I already did 50. I am disappointed in the way it feels. It’s just coil for resistance but it feels like I’m barely working. Doing weighted calf raises or even calf raises on a leg press machine or seated calf raise machine feel so much more challenging than this coil based resistance device.